The place was a small clearing in the center of a palm grove. In this was one of those boiling mud geysers which I have already described. Around its edge were scattered a number of leathern thongs cut from iguanodon hide, and a large collapsed membrane which proved to be the dried and scraped stomach of one of the great fish lizards from the lake. This huge sack had been sewn up at one end and only a small orifice left at the other. Into this opening several bamboo canes had been inserted and the other ends of these canes were in contact with conical clay funnels which collected the gas bubbling up through the mud of the geyser. Soon the flaccid organ began to slowly expand and show such a tendency to upward movements that Challenger fastened the cords which held it to the trunks of the surrounding trees. In half an hour a good-sized gasbag had been formed, and the jerking and straining upon the thongs showed that it was capable of considerable lift. Challenger, like a glad father in the presence of his firstborn, stood smiling and stroking his beard, in silent, self-satisfied content as he gazed at the creation of his brain. It was Summerlee who first broke the silence.